[jdk17] RFR: 8267952: async logging supports to dynamically change tags and decorators

[Xin Liu]

This patch fixed intermittent crashes of gtest/AsyncLogGtest.java. The root cause 
is that previous flush() can't guarantee flush all pending messages in AsyncLog
buffer. This patch implements flush() using a synchronizaton token and waits for
completion. This approach isn't MT-safe but it can serialize all flush() calls in
a thread. 

Two concurrent tests are appended to cover the hazard cases.
This patch also comments LogConfiguration::configure_output() MT-safety.

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Commit messages:
 - 8267952: async logging supports to dynamically change tags and decorators

Changes: https://git.openjdk.java.net/jdk17/pull/130/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17&pr=130&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8267952
  Stats: 195 lines in 9 files changed: 159 ins; 14 del; 22 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/130.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/130/head:pull/130

PR: https://git.openjdk.java.net/jdk17/pull/130